bush, laura bush, former secretary of state hillary clinton all left washington from andrews air force base on "air force one." president clinton and jimmy carter will be meeting them in south africa. president obama will be speaking at tomorrow's memorial service. nbc's ron allen live in soweto. ron, this is a gathering of the great, families, people of south africa all gathering. you have covered this so long. tell me about the emotions as people in south africa prepare? >>. >> reporter: it's an unbelievable atmosphere. we're across the street from the nelson mandela home, the home occupied from 1940s to 1990s. tomorrow is a day that will be unlike any other. there's more than 80 heads of state here. that will surpass the heads of state and world leaders who came to mourn and to say good-bye to pope john paul ii. largest gathering of heads of state outside of u.n. perhaps ever. we'll have to see how this day goes. and of course, there will be tens of thousands of people, perhaps millions of people, trying to get near the soccer stadium where this event will take place. it begins at 1